Re: [VAC] Epoxy testimonial, brothers and sisters...

[Rob Super <rms@xxxxxxxxxx>]

Sister Annie:

There are many different epoxy formulations, each with its own intended 
use. One of the important variables is the "pot life": the amount of time 
you have between thoroughly mixing the components and the point where it 
sets up too much to be usable. For some applications you want a 
fast-setting formula (= short pot life), but for wood consolidation you 
need something slower. Not only so you have longer to work with it, but 
also so it has plenty of time, after application but before hardening, to 
soak deeply into the wood.

It's important to mix the 2 parts (resin and hardener) in the specified 
ratio. Using a little less hardener than called for *may* extend the pot 
life but will almost certainly result in a mix that never fully 
hardens--bad news. Some products can be modified by adding a special 
accelerant or retarder, but its easier to begin with a product that's 
designed for the particular use. Right or wrong, I have a non-safety 
concern re thinning with lacquer thinner. Thinning means less of the 
product you want (epoxy) per unit volume of the finished product (the 
consolidated wood). It will be weaker. Better to get penetration by using 
a product that is designed to soak into wood and has time to do so. The 
manufacturer I happen to have used with great success for a number of 
years is Abatron. I usually get about 20 minutes of pot life with their 
"Liquid Wood". (Check 'em out @ "abatron.com".)

Variables that do affect pot life are temperature (the hotter the day the 
faster the mix will set up) and and how much you mix at a time. If you 
mix a large quantity the mass holds more heat as the reaction begins, the 
increased heat speeds the reaction, the faster reaction generates more 
heat, etc, and pretty soon you have a thermonuclear situation. (Well, it 
*can* get pretty hot--at which point there is nothing to be done but stop 
work and marvel at the wonders of chemistry.) Some manufacturers' 
instructions include guidelines on these effects (also humidity), but 
generally speaking its best to work in the cool of the day and to and mix 
more, but smaller, batches.

"Thus endeth the lesson for today. Go forth and restore" :-)#

Rob